Field of the Invention
The present invention relates to a capo for a stringed instrument such as a guitar or banjo. Particularly, the capo is intended to be able to adapt to the curvature of a finger board and/or strings to which it is applied.
Description of Related Art
A capo (sometimes referred to as a capodastro, capodaster, capotasto or cejilla) is a well-known device used with a stringed instrument having a neck and a set of strings extending along the length of the neck. The capo, when applied to an instrument neck, serves to clamp the strings against a finger board and, in particular, between or against one of the number of fret bars disposed along the length of finger board. In practice, a capo serves to reduce the effective length of the strings and therefore adjust the pitch; i.e. the pitch is raised as the effective length of a string is shortened.
A large number of different capo types are known, each of which has a different advantage or technical consideration. However, most standard capo designs feature a relatively rigid clamping bar which reaches over the strings in order to apply downward pressure thereon. The clamping bar is usually a metal material with a rubber contact surface which has some resilience in order to accommodate strings and any minor curve across the instrument's neck. However, guitar finger boards vary in the radius that is desirable, ranging from flat on a classical style instrument to a radius of approximately 7.25 inches (18.4 cm) on some electric guitars. Many contemporary steel-string acoustic guitars have a radius across the finger board of 12 to 16 inches (30.5 to 40.6 cm). It is also known to apply a varying (compound) radius along the length of the finger board.
The radius of a finger board is also affected by the gauge of strings used on the instrument. For example, as illustrated in FIG. 1 of the accompanying drawings, a guitar neck N is shown having a finger board B and associated fret F with a radius which is effectively offset to one side by the gauge of the strings which increase in diameter (in order to produce lower frequencies) from right to left across the six strings S. The configuration could be reversed dependent on whether the instrument is left or right handed. As will be noted by a skilled person, FIG. 1 effectively shows all strings S pressed against fret F of the finger board B, as if with a capo applied.
It will be apparent that the radius of any capo clamping arm designed for pressing with even pressure against the finger board/fret, to enable strings to come into solid contact with a fret and avoid any “buzzing” of the strings, must take this into account. A common way for capo makers to address this problem is to use a resilient material such as rubber to press onto the strings. This allows the strings to press into the rubber locally and at a relatively even pressure between the strings. However, it is well known that this approach is only partially effective and can result in too much pressure on some strings, leading to sharp notes. Alternatively, insufficient pressure can result in unwanted vibrations or “buzzing”.
The player may compensate for the above by adjusting the tuning, although clearly this is not ideal because it would prohibit a quick changeover during a performance when applying the capo or adjusting its position along the guitar neck.
The use of softer rubber can provide more flexibility/accommodation in the capo properties and adaptability to different curvatures, but soft rubber is also known to deaden the tone of guitar strings to some extent.
In an effort to address varying neck radius and string gauge US20160247490 proposes a capo incorporating a fluid insert to be located behind a string contacting pad such that the relatively incompressible nature of the fluid adapts a curvature of the string contacting pad (made of a resilient but relatively hard material) to match the combined curvature of the strings and instrument finger board itself. This solution, while effective, requires the fluid to be housed and incorporated with the capo clamp arm which complicates the manufacturing process.